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  1. #1
    Peter C's Avatar
    Peter C Guest

    Default mtf of moon edge



    Hi,

    I heard that high spatial frequency such as moon edge, cassini's
    division, double stars would have better contrast
    in a scope with 33% central obstruction because the
    disc is smaller. But the surrounding rings are brightened so they
    would intrude on the neighboring details making it lose contrast. I
    can't find a satisfactory explanation in the web site with
    illustration how it can improve the contrast.
    Imagine the moon edge with black and white details.
    The tinier disc has brighter diffraction rings that can
    make the black and white moon edge greyish, so how
    can it have better contrast. Thanks!

    Pete

  2. #2
    Peter C's Avatar
    Peter C Guest

    Default mtf of moon edge

    On May 8, 4:51 pm, Peter C <petercrisc...@gmail.com> wrote:

    After researching a lot, I found out the answer is thus:
    Because if the central disc is smaller, you can resolve
    two smaller points. And when youu can resolve better,
    the contrast would automatically be better. It follows?

    It's being able to resolve stars inside the Cassini's
    Division when there is central obstruction.
    Hmm... I wonder how many stars can be seen thru
    Saturn Cassini's division which is a hole, please show me
    pictures of one. Tnx.

    Pete

 

 

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